GNOME 2.91.5 is today's development release after the 2.91.4 release was previously skipped from making it out there due to blocking bugs during a collision with the holidays.
Vincent says about this GNOME 3.0 desktop preview, "It's working quite well, and the rough edges we had for 3.0 are all disappearing with time, which is good! But of course, it's not perfect yet :-) The good news is that we still have quite some time to reach perfection. Yes, that's our goal!"
The GNOME 2.91.5 release announcement with links to the various GNOME modules making up this inaugural 2011 development version can be found on the gnome-announce-list.
GNOME 3.0 will be released in March, but no worries as there are still a few more development builds before reaching that milestone.